1. Field of the Invention
The present invention relates to an actinic ray-sensitive or radiation-sensitive resin composition preferably used in super-micro-lithography process such as the manufacture of super LSI and high capacity microchips and other photo-fabrication processes, a resist film formed with the composition, and a pattern-forming method using the same. More specifically the invention relates to a positive resist composition for electron beam, X-ray or EUV ray, a pattern-forming method using the same, and a resin for use in a positive resist composition.
2. Description of the Related Art
In manufacturing process of semiconductor devices such as IC and LSI, fine process by lithography with a photoresist composition has been conventionally carried out. In recent years, ultrafine pattern formation of a sub-micron region and a quarter micron region has been required with higher integration of integrated circuits. In such a circumstance, exposure wavelength also shows a tendency to become shorter such as from a g line to an i line, and further to a KrF excimer laser ray. Further, besides a KrF excimer laser ray, development of lithography using an electron beam, an X-ray or an EUV ray is also now progressing.
In particular, electron beam lithography is positioned as a pattern-forming technique of the next generation or the next of the next generation, and positive resist of high sensitivity and high resolution is desired. For shortening the processing time of wafers, increase of sensitivity is a particularly important problem. However, pursuit of higher sensitization in positive resist for electron beams is accompanied by not only lowering of resolution but also deterioration of line edge roughness, accordingly development of a resist satisfying these characteristics at the same time is strongly desired. Here, line edge roughness means that, since the edge at the interface between the pattern of a resist and a substrate irregularly fluctuates in the perpendicular direction to the line direction attributably to the characteristics of the resist, the edge is seen unevenly when the pattern is viewed just above. This unevenness is transferred in the etching process of using the resist as a mask and deteriorates electric characteristics to lower the yield. In particular, in a super fine region of 0.25 μm or less, line edge roughness is an extremely important problem to be improved. High sensitivity, high resolution, good pattern form and good line edge roughness are in a relationship of tradeoff, and it is very important how to satisfy these characteristics at the same time.
It is also an important problem to satisfy high sensitivity, high resolution, good pattern form and good line edge roughness at the same time in lithography using X-rays and EUV rays, and solution is necessary.
As one way of solving these problems, use of a resin having a photo-acid generator in the main chain or side chain of a polymer is examined (JP-A-9-325497 (The term “JP-A” as used herein refers to an “unexamined published Japanese patent application”.), JP-A-10-221852, JP-A-2006-178317, JP-A-2007-197718, WO 2006/121096, US 2006/121390, US 2007/117043, JP-A-2008-133448 and Proc. of SPIE, Vol. 6923, 692312, 2008). However, in the examination of JP-A-9-325497, since the composition is a mixed system of a resin having a photo-acid generator and a dissolution-inhibiting compound capable of increasing solubility in an alkali developer by decomposition due to an acid, it is difficult to obtain good pattern form and line edge roughness attributable to a heterogeneous mixing property of these materials.
On the other hand, in JP-A-10-221852, JP-A-2006-178317, JP-A-2007-197718, WO 2006/121096 and US 2006/121390, resins having a photo-acid generating group and a group capable of decomposing by the action of an acid and increasing the solubility in an alkali developer in the same molecule are disclosed, but it cannot be said that the sensitivity to electron beams, X-rays or EUV rays is sufficient.
Further, a terpolymer comprising hydroxystyrene, acrylate containing an adamantyl group and acrylate containing a photo-acid generator is disclosed in US 2007/117043 and Proc. of SPIE, Vol. 6923, 692312, 2008. JP-A-2008-133448 discloses a high energy ray- or heat-sensitive resist containing a resin containing a repeating unit capable of generating a sulfonic acid at the fluorine-containing terminal of a side chain for improving high resolution, iso/dense bias and exposure margin.
On the other hand, in electron beam, X-ray or EUV ray lithography, the volatile constituent from a resist film at exposure time causes contamination of a very expensive exposing apparatus as outed gas. However, if a large amount of a solvent having a high boiling temperature is used as a resist solvent, the solvent remains in the film and causes outgassing. Accordingly, the development of a resin component capable of dissolving and coating in a general purpose solvent having a low boiling temperature as far as possible is desired.
Thus, it is the present situation that high sensitivity, high resolution, good pattern form, good line edge roughness and outgassing performance are not sufficiently satisfied at the same time in electron beam, X-ray or EUV ray lithography by the combinations of the presently known techniques.
In addition, fine processing with a resist composition is not only directly used in the manufacture of integrated circuit but also it is applied to the manufacture of a mold structure for what is called imprinting in recent years (e.g., refer to JP-A-2004-158287, JP-A-2008-162101 and Fundamentals, Technical Development and Development of Applications of Nano-Imprinting—Techniques on Substrates And The Latest Technical Development of Nano-Imprinting—, compiled by Yoshihiko Hirai, published by Frontier Publishing Company (June, 2006)). Therefore, even when X-ray, soft X-ray or electron beam is used as an exposure light source, it is important problems to satisfy high sensitivity, high resolution, good pattern form, good line edge roughness and outgassing performance at the same time, and resolution of these problems is necessary.